Gearbox assemblies with idler gears

Abstract

A gear assembly for use with a turbomachine comprises a sun gear, a plurality of planet gears, and a ring gear. The gear assembly is connected to an input shaft and an output shaft. The sun gear is configured to rotate about a longitudinal centerline of the gear assembly, and is driven by the input shaft. A component of the gear assembly drives the output shaft. The gear assembly further comprises an output shaft reversal mechanism configured to reverse the rotational direction of the output shaft.

1 . A turbomachine engine comprising:
 a fan assembly comprising a plurality of fan blades;   a core engine comprising a turbine;   an input shaft rotatable with the turbine and configured to rotate in a first rotational direction; and   a gear assembly that receives the input shaft at a first speed and drives an output shaft coupled to the fan assembly at a second speed, the second speed being slower than the first speed, the gear assembly comprising:
 a sun gear coupled to the input shaft and configured to rotate in the first rotational direction; 
 a plurality of idler gears engaged with the sun gear and being configured to rotate in a second rotational direction, the second rotational direction being opposite the first rotational direction; 
 a plurality of planet gear layshafts that each support a first stage planet gear and a second stage planet gear, the plurality of idler gears engaged with respective ones of the first stage planet gears; and 
 a ring gear engaged with the second stage planet gears and configured to drive the output shaft in the first rotational direction. 
   
     
     
         2 . The turbomachine engine of  claim 1 , wherein the gear assembly has a gear ratio that is in the range of 5:1-14:1. 
     
     
         3 . The turbomachine engine of  claim 1 , wherein the gear assembly has a gear ratio that is in the range of 6:1-12:1. 
     
     
         4 . The turbomachine engine of  claim 1 , wherein the gear assembly has a gear ratio that is in the range of 7:1-10:1. 
     
     
         5 . The turbomachine engine of  claim 1 , wherein the gear assembly has a gear ratio that is in the range of 8:1-9:1. 
     
     
         6 . The turbomachine engine of  claim 1 , wherein the fan assembly is a single stage of unducted fan blades. 
     
     
         7 . The turbomachine engine of  claim 1 , wherein there are three planet gear layshafts. 
     
     
         8 . The turbomachine engine of  claim 1 , wherein the gear assembly has an axial envelope (Ae) and a radial envelope (Re), the gear assembly has a gear ratio that is in the range of 6:1 to 12:1, and a ratio of Re/Ae for the gear assembly is in the range of 1.26 to 3.66. 
     
     
         9 . The turbomachine engine of  claim 1 , wherein the gear assembly has an axial envelope (Ae) and a radial envelope (Re), the gear assembly has a gear ratio that is in the range of 7:1 to 10:1, and a ratio of Re/Ae for the gear assembly is in the range of 1.79 to 3.05. 
     
     
         10 . An aircraft comprising:
 a first turbofan engine having a first core engine, a first input shaft, a first gear assembly, and a first output shaft that is configured to drive a first fan assembly, the first core engine being configured to drive the first input shaft in a first rotational direction, and the first gear assembly being configured to drive the first output shaft in a second rotational direction that is opposite the first rotational direction so that the first fan assembly is configured to rotate in the second rotational direction; and   a second turbofan engine having a second core engine, a second input shaft, a second gear assembly, and a second output shaft that is configured to drive a second fan assembly, the second core engine being configured to drive the second input shaft in the first rotational direction, and the second gear assembly being configured to drive the second output shaft in the first rotational direction so that the second fan assembly rotates in the first rotational direction,   wherein the second gear assembly comprises:
 a sun gear coupled to the input shaft and configured to rotate in the first rotational direction; 
 a plurality of idler gears engaged with the sun gear and being configured to rotate in the second rotational direction; 
 a plurality of planet gear layshafts that each support a first stage planet gear and a second stage planet gear, the plurality of idler gears engaged with respective ones of the first stage planet gears; and 
 a ring gear engaged with the second stage planet gears and configured to drive the output shaft in the first rotational direction, 
   wherein the first fan assembly and second fan assembly are configured to rotate in opposite rotational directions with the first fan assembly being configured to rotate in the second rotational direction and the second fan assembly being configured to rotate in the first rotational direction.   
     
     
         11 . The aircraft of  claim 10 , wherein the second gear assembly has a gear ratio that is in the range of 5:1-14:1. 
     
     
         12 . The aircraft of  claim 10 , wherein the second gear assembly has a gear ratio that is in the range of 6:1-12:1. 
     
     
         13 . The aircraft of  claim 10 , wherein the second gear assembly has a gear ratio that is in the range of 7:1-10:1. 
     
     
         14 . The aircraft of  claim 10 , wherein the gear assembly has a gear ratio that is in the range of 8:1-9:1. 
     
     
         15 . The aircraft of  claim 10 , wherein the second fan assembly is a single stage of unducted fan blades. 
     
     
         16 . The aircraft of  claim 10 , wherein the second gear assembly has three planet gear layshafts. 
     
     
         17 . The aircraft of  claim 10 , wherein the second gear assembly has an axial envelope (Ae) and a radial envelope (Re), the gear assembly has a gear ratio that is in the range of 6:1 to 12:1, and a ratio of Re/Ae for the gear assembly is in the range of 1.26 to 3.66. 
     
     
         18 . The aircraft of  claim 10 , wherein the second gear assembly has an axial envelope (Ae) and a radial envelope (Re), the gear assembly has a gear ratio that is in the range of 7:1 to 10:1, and a ratio of Re/Ae for the gear assembly is in the range of 1.79 to 3.05. 
     
     
         19 . The aircraft of  claim 10 , wherein the first gear assembly has the same gear ratio as the second gear assembly. 
     
     
         20 . The aircraft of  claim 10 , further comprising:
 a third turbofan engine having a third core engine;   a fourth turbofan engine having a fourth core engine;   wherein the third turbofan engine has a third fan assembly that rotates in the second rotational direction, and the fourth turbofan engine has a fourth fan assembly that rotates in the first rotational direction.